Various intervention techniques have been developed to treat narrowings in blood vessels, allowing increased blood flow through the vessels. One technique for treating stenosis or occlusion of a blood vessel is balloon dilatation, or percutaneous transluminal angioplasty (PTA). Generally, an arterial sheath is introduced through a puncture or incision in the patient's skin to provide percutaneous access to blood vessels. This is followed by insertion of a balloon catheter through the arterial sheath and its advancement through the blood vessels to the target site, where the stenosis is then dilated. PTA catheters are commonly guided through blood vessels by thin wires called guidewires, which may be either solid or hollow. To provide radial support to the treated vessel in order to prolong the positive effects of PTA, a stent may be implanted in conjunction with the procedure.
Thrombectomy is a minimally invasive technique for removal of an entire thrombus or a sufficient portion of the thrombus to enlarge the stenotic or diseased blood vessel and may be accomplished instead of a PTA procedure. Atherectomy is another well-known minimally invasive procedure that mechanically cuts or abrades a stenosis within the diseased portion of the vessel. Alternatively, ablation therapies use laser or RF signals to superheat or vaporize a thrombus within the vessel.
During each of these procedures, there is a risk that emboli dislodged by the procedure will migrate through the circulatory system and cause ischaemic events, such as infarction or stroke. Thus, clinicians have approached prevention of escaped emboli through use of occlusion devices, filters, lysing, and aspiration techniques. For example, it is known to remove the embolic material by suction through an aspiration lumen in the treatment catheter or by capturing emboli in a filter or occlusion device positioned distal of the treatment area. The terms “distal” and “proximal” are used herein with respect to the treating clinician: Distal or distally refer to elements distant from, or a direction away from the clinician, and proximal or proximally, refer to elements closer to, or a direction towards the clinician.
A difficulty associated with combing angioplasty with embolic protection is the limited time available to perform the procedure. That is, in order to contain emboli produced during intravascular therapy, the vessel may be occluded, meaning that no blood perfuses through the vessel to the end organ. Thus, depending upon the patient's vasculature and the organ involved, the complete procedure may need to be completed within just a few minutes.
Known embolic protection guidewires comprise an inflatable occlusion balloon located adjacent the distal end of a hollow guidewire. Dilute radiopaque contrast liquid is forced through the guidewire lumen to inflate and deflate the occlusion balloon. However, operating the balloon may take longer than desired due to the viscosity of the inflation medium, the small size of the inflation lumen, and the requirement to attach, detach and operate one or more inflation accessories at the proximal end of the guidewire.
U.S. Pat. No. 6,312,407 B1 teaches mechanically operated occlusion devices that may function more quickly than occlusion balloons, thus saving time during the treatment procedure. However, some mechanical occluder designs are complex and costly to produce.
Another known type of embolic protection guidewire comprises a filter located adjacent the distal end of the guidewire. A filter guidewire may include a slidable sheath to restrain a self-expanding filter during delivery and retrieval of the device. Alternatively, a filter apparatus may be mechanically expandable and collapsible, using push-pull operation of coaxially sliding inner and outer shafts to translocate the ends of the filter. However, known filter arrangements may be complex to make or operate, or they may have an undesirably large collapsed profile, which can limit the filter's ability to cross tight stenoses. Accordingly, there is a need for a simplified, low-profile embolic protection device.